Technical Field
The invention relates to a triple sealing seat with gas flushing for a conduit gate valve having the features described herein and outlined in the pending claims, as well as a conduit gate valve for chemical and petrochemical plants, and a method for sealing a shut-off plate of a conduit gate valve.
Description of Related Art
Sealing seats for conduit gate valves are known from the prior art. Patent document EP 0 932 780 B1 should be mentioned here as an example. The conduit gate valve disclosed herein is a single-plate pipe gate valve featuring a shut-off plate which is displaceable between an open and a closed position within the conduit gate valve's housing. This conduit gate valve is employed in chemical, in particular petrochemical plants and, by way of example, serves the purpose of obturating a coking drum. In this case, a sealing ring resting against the circumference of the shut-off plate in the closed position of the conduit gate valve is pre-stressed by spring elements and pressed against the shut-off plate so as to seal the conduit gate valve.
This construction has several drawbacks. On the one hand, the seal formed in this way is composed of several structural parts, a fact which complicates the installation and removal accordingly. Furthermore, the sealing surfaces of the sealing ring wear easily during displacement of the shut-off plate since they are pressed against the shut-off plate by the spring elements and exposed to abrasion. The spring elements themselves wear also and may lead to failure of the sealing function. Of particular importance are here also leakages with respect to gases which are formed during the coking process and may enter the interior of the conduit gate valve's housing.